dementia prevalence

Falling in British dementia rate

A survey of 7796 older adults (65+) living in three geographic areas in England has allowed us to compare dementia rates over time, with an identical survey having been taken between 1989 and 1994. The overall prevalence of dementia fell significantly, from 8.3% to 6.5%.

The finding provides further evidence that a cohort effect exists in dementia prevalence.

http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2813%2961570-6/fulltext

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Diagnosis and prevalence of dementia & MCI — recent reports

August, 2011

Several recent reports point to the need for GPs to be better informed about the initial symptoms of dementia and mild cognitive impairment.

Functional impairment good indicator of mild cognitive impairment

Evaluation of 816 older adults, of whom 229 had no cognitive problems, 394 had a diagnosis of amnestic mild cognitive impairment, and 193 had a diagnosis of mild Alzheimer’s, has revealed that most of those with aMCI (72%) or AD (97%) had trouble with at least one type of function on the Pfeffer Functional Activities Questionnaire. Only 8% of controls had any difficulty. In both impaired groups, those who had the most difficulty functioning also tended to score worse on cognition tests, have smaller hippocampal volumes, and carry the APOe4 gene.

Two of the ten items in the questionnaire were specific in differentiating the control group from the impaired groups. Those items concerned "remembering appointments, family occasions, holidays, and medications” and "assembling tax records, business affairs, or other papers." Only 34% of those with aMCI and 3.6% of those with AD had no difficulty with these items.

The findings suggest that even mild disruptions in daily functioning may be an important clinical indicator of disease.

Early-onset Alzheimer’s poorly diagnosed when initial symptoms aren’t memory related

Post-mortem analysis of 40 people diagnosed  with early-onset Alzheimer’s has revealed that about 38% experienced initial symptoms other than memory problems, such as behavior, vision or language problems and a decline in executive function, or the ability to carry out tasks. Of these, 53% were incorrectly diagnosed when first seen by a doctor, compared to 4% of those who had memory problems. Of those with unusual initial symptoms, 47% were still incorrectly diagnosed at the time of their death.

The mean age at onset was 54.5 years (range 46-60). The average duration of the disease was 11 years, with an average diagnostic delay of 3 years.

GPs misidentify and fail to identify early dementia and MCI

A review of 30 studies involving 15,277 people seen in primary care for cognitive disorders, has found that while GPs managed to identify eight out of ten people with moderate to severe dementia, they only identified 45% of those with early dementia and mild cognitive impairment. Moreover, they were very poor at recording such diagnoses. Thus, though they recognized 45% of the MCI cases, they only recorded 11% of these cases in their medical notes. Although they identified 73% of people with dementia, they made correct annotations in medical records in only 38% of cases.

But the problem is not simply one of failing to diagnose — they were even more likely to misidentify dementia, and this was particularly true for those with depression or hearing problems.

The findings point to the need for more widespread use of simple cognitive screening tests.

Prevalence of dementia & MCI in 'oldest old' women

Data from 1,299 women enrolled in the Women Cognitive Impairment Study of Exceptional Aging suggests that the incidence of dementia almost doubles with every 5 years of age and prevalence rises from approximately 2-3% in those 65 to 75 years to 35% in those 85+.

Among those with mild cognitive impairment, amnestic multiple domain was most common (34%), followed by non-amnestic single domain (29%). Amnestic single domain (affecting only one type of cognitive function, including memory difficulty) affected 22%.

Alzheimer's disease and mixed dementia accounted for nearly 80% of dementia cases, and vascular dementia for 12.1%.

Those with dementia tended to be older, less likely to have completed high school, more likely to have reported depression, a history of stroke, and to have the APOEe4 gene.

The women in the study had an average age of 88.2 years and 27% were older than 90. 41% had clinical cognitive impairment (17.8% with dementia and 23.2% with mild cognitive impairment).

The high prevalence of cognitive impairment in this age group points to the importance of screening for cognitive disorders, particularly among high-risk groups.

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70-year-olds smarter than they used to be

November, 2010

Findings from a large Swedish study are consistent with the hypothesis that more education and better healthcare have produced less cognitive impairment in present-day older adults.

Beginning in 1971, healthy older adults in Gothenburg, Sweden, have been participating in a longitudinal study of their cognitive health. The first H70 study started in 1971 with 381 residents of Gothenburg who were 70 years old; a new one began in 2000 with 551 residents and is still ongoing. For the first cohort (born in 1901-02), low scores on non-memory tests turned out to be a good predictor of dementia; however, these tests were not predictive for the generation born in 1930. Those from the later cohort also performed better in the intelligence tests at age 70 than their predecessors had.

It’s suggested that the higher intelligence is down to the later cohort’s better pre and postnatal care, better nutrition, higher quality education, and better treatment of high blood pressure and cholesterol. And possibly the cognitive demands of modern life.

Nevertheless, the researchers reported that the incidence of dementia at age 75 was little different (5% in the first cohort and 4.4% in the later). However, since a substantially greater proportion of the first cohort were dead by that age (15.7% compared to 4.4% of the 2nd cohort), it seems quite probable that there really was a higher incidence of dementia in the earlier cohort.

The fact that low scores on non-memory cognitive tests were predictive in the first cohort of both dementia and death by age 75 supports this argument.

The fact that low scores on non-memory cognitive tests were not predictive of dementia or death in the later cohort is in keeping with the evidence that higher levels of education help delay dementia. We will need to wait for later findings from this study to see whether that is what is happening.

The findings are not inconsistent with those from a very large U.S. national study that found older adults (70+) are now less likely to be cognitively impaired (see below). It was suggested then also that better healthcare and more education were factors behind this decline in the rate of cognitive impairment.

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A new nationally representative study involving 11,000 people shows a downward trend in the rate of cognitive impairment among people aged 70 and older, from 12.2% to 8.7% between 1993 and 2002. It’s speculated that factors behind this decline may be that today’s older people are much likelier to have had more formal education, higher economic status, and better care for risk factors such as high blood pressure, high cholesterol and smoking that can jeopardize their brains. In fact the data suggest that about 40% of the decrease in cognitive impairment over the decade was likely due to the increase in education levels and personal wealth between the two groups of seniors studied at the two time points. The trend is consistent with a dramatic decline in chronic disability among older Americans over the past two decades.

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Career choice may determine where frontotemporal dementia begins

October, 2010
  • An international review of patients with frontotemporal dementia has revealed that the area of the brain first affected tends to be the hemisphere least used in the individual’s occupation.

A review of brain imaging and occupation data from 588 patients diagnosed with frontotemporal dementia has found that among the dementias affecting those 65 years and younger, FTD is as common as Alzheimer's disease. The study also found that the side of the brain first attacked (unlike Alzheimer’s, FTD typically begins with tissue loss in one hemisphere) is influenced by the person’s occupation.

Using occupation scores that reflect the type of skills emphasized, they found that patients with professions rated highly for verbal skills, such as school principals, had greater tissue loss on the right side of the brain, whereas those rated low for verbal skills, such as flight engineers, had greater tissue loss on the left side of the brain. This effect was expressed most clearly in the temporal lobes of the brain. In other words, the side of the brain least used in the patient's professional life was apparently the first attacked.

These findings are in keeping with the theory of cognitive reserve, but may be due to some asymmetry in the brain that both inclines them to a particular occupational path and renders the relatively deficient hemisphere more vulnerable in later life.

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Dementia rate in extreme elderly population

February, 2010

Data from The 90+ Study has revealed a sharply increasing incidence rate for dementia, from nearly 13% per year for 90-94, to over 40% in the 100+ age group.

Data from 330 participants in The 90+ Study, of whom 70% were women, has revealed an overall annual incidence rate of 18.2% for dementia, rising from 12.7% per year in the 90-94 age group, to 21.2% in the 95-99 age group and 40.7% per year in the 100+ age group. 60% of the cases were attributed to Alzheimer's disease, 22% vascular dementia, 9% mixed Alzheimer’s and vascular dementia and 9% other/unknown. Unlike previous findings, rates were very similar for men and women.

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